Combination of Phase and Frequency Correlation in the Brillouin Dynamic Grating Sensor to Achieve Millimeter Spatial Resolution Over 17 km of Optical Fiber

Extensive applications of distribution fiber sensors in various industries have led researchers to make great efforts to improve the properties of these sensors. Spatial resolution and sensing length are considered among the most important parameters in fiber optic distribution sensor by engineers and users of these sensors. Among these fiber sensors, Rayleigh scattering-based sensors due to their very long sensing length and Brillouin scattering sensors due to their high spatial resolution, each cover a specific range of applications. Among Brillouin sensors, Brillouin dynamic grating (BDG) sensor has the highest spatial resolution, but the short sensing length of this sensor is one of its major disadvantages. For this reason, trying to increase the sensing length in this sensor is one of the priorities for researchers in this field. In this paper, using a new method called the combination of phase and frequency correlation, the maximum sensing length in the BDG sensor is simulated for spatial resolution in the range of millimeters. The simulation results show that with the help of this sensor, a spatial resolution of 9 mm over 17.7 km of the measurement fiber can be achieved.